Enhanced Sintered Silver for SiC Wide Bandgap Power Electronics Integrated Package Module

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Mei-Chien Lu
Keyword(s):  
High Temperature ◽  
Power Electronics ◽  
Technology Implementation ◽  
Wide Bandgap ◽  
Void Coalescence ◽  
Thermal Interface Materials ◽  
Die Attach ◽  
And Performance ◽  
Interface Materials ◽  
Sintered Silver

Thermal interface materials (TIMs) are crucial elements for packaging of power electronics. In particular, development of high-temperature lead-free die-attach TIMs for silicon carbide wide bandgap power electronics is a challenge. Among major options, sintered silver shows advantages in ease of applications. Cost, performance, reliability, and integration are concerns for technology implementation. The current study first discusses issues and status reported in literatures. Then it focuses on cost reduction and performance improvement of sintered silver using enhancement structures at micro- and nano-scales. A few design architectures are analyzed by finite element methods. The feasibility of strengthening edges and corners is also assessed. The downside of potential increase of unfavorable stresses to accelerate void coalescence would be optimized in conjunction with design concept of power electronics package modules for paths of solutions in the form of integrated systems. Demands of developing new high-temperature packaging materials to enable optimized package designs are also highlighted.

Thermal Interface Materials Enhanced by Micro and Nanostructures

2018 ◽  
Author(s):  
Mei-Chien Lu
Keyword(s):  
Power Electronics ◽  
Technology Implementation ◽  
Wide Bandgap ◽  
Void Coalescence ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Die Attach ◽  
Module Systems ◽  
Interface Materials ◽  
Sintered Silver

Thermal Interface materials are crucial elements for packaging of power electronics. In particular, development of high temperature lead free die-attach thermal interface materials for silicon carbide wide bandgap power electronics is a challenge. Failures of power electronics package modules often occur at die-attach areas. Among major options, sintered silver shows advantages in ease of applications. Cost, reliability, and integration are concerns for technology implementation. The current study first discusses issues and status reported in literatures. Then it focuses on cost reduction and improvement of sintered silver using enhancement structures at micro and nano scales. A few design architectures are analyzed by finite element methods. The feasibility of strengthening edges and corners is also assessed. The downside of potential increase of unfavorable stresses to accelerate void coalescence would be discussed in conjunction with design concept of power electronics package modules for paths of solutions in the form of integrated module systems.

scholarly journals Degradation of thermal interface materials for high-temperature power electronics applications

2013 ◽  
Vol 53 (12) ◽  
pp. 1933-1942 ◽  
Author(s):  
R. Skuriat ◽  
J.F. Li ◽  
P.A. Agyakwa ◽  
N. Mattey ◽  
P. Evans ◽  
...  
Keyword(s):  
High Temperature ◽  
Power Electronics ◽  
Thermal Interface Materials ◽  
Thermal Interface ◽  
Interface Materials

Shear Strength and Thermomechanical Reliability of Sintered Ag Joints Containing low CTE Non-metal Additives for Die Attach

2018 ◽  
Vol 2018 (1) ◽  
pp. 000167-000172
Author(s):  
Guangyu Fan ◽  
Christine Labarbera ◽  
Ning-Cheng Lee ◽  
Colin Clark
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Thermal Cycling ◽  
Power Electronics ◽  
Metal Particles ◽  
Mechanical Reliability ◽  
Die Attach ◽  
Silver Sinter ◽  
Metal Additives ◽  
Sintered Silver

Abstract Ag sintering has been paid attention as an alternative to soldering in die attach for decades, especially for high temperature power electronics packages because of its high melting temperature, highly thermal and electrical conductivity of the sintered silver joints, and low process temperature less than 275°C. The coefficient of thermal expansion (CTE) of silver (19.1ppm/°C), however, is much higher than the silicon die (2.6ppm/°C) and the commonly used alumina substrate (7.2ppm/°C). CTE mismatch of the different materials in the various components in a power electronics package lead to the delamination at the interface between interconnection layer and chips or substrate, and/or cracking of the interconnection layer is one of the mostly common causes of failure of power electronics device during thermal cycling or high temperature operation. In recent years we have been developing a series of silver sinter pastes containing low CTE non-metal particles to reduce or adjust CTE of the sintered joints so as to extend the lifetime and reliability of power electronics device in high temperature applications. In the present paper, we will report a new set of silver sinter pastes containing micro scale non-metal particles, a sintering process, microstructural morphologies, thermo-mechanical reliability of the sintered joint and effect of the contents of non-metal particles on shear strength of the sintered silver joints bonding an Ag silicon die on Ni/Au DBC substrates. Shear tests on the sintered joints with and/or without the low CTE non-metal additives have been conducted at room temperature, 200, 250, and 300°C. Thermo-mechanical reliability of the sintered joints was evaluated by thermal cycling, thermal shock, high temperature storage tests (HTS), respectively. X-ray inspection and scanning electronic microscopy (SEM) were used to characterize void, crack and microstructure morphologies of the sintered joints with and/or without the additives.

Mechanical Insertion and Reliability Testing of Thermal Interface Materials for Semiconductor Test and Burn-in Applications

2019 ◽  
Vol 2019 (1) ◽  
pp. 000584-000590
Author(s):  
Dave Saums ◽  
Tim Jensen ◽  
Carol Gowans ◽  
Seth Homer ◽  
Ron Hunadi
Keyword(s):  
Performance Test ◽  
Thermal Interface Materials ◽  
Test Procedures ◽  
Thermal Interface ◽  
Semiconductor Test ◽  
New Material ◽  
And Performance ◽  
And Control ◽  
Interface Materials

Abstract Very challenging requirements exist for thermal interface materials (TIMs) for demanding applications I semiconductor testing. Reliability requirements and multiple contact cycling requirements are substantially different and do not exist in traditional applications for TIMs. Developing new material types to meet these very exacting and unusual requirements has been a long-term goal and requires development of an unusual series of test procedures to demonstrate whether the desired reliability goals have been met. Use of a servo-driven, commercial test stand that has unique features for operation and control is described as the basis for a reliability and performance test program developed for these new materials in three phases, with new data for a fourth test phase added, and comparative values for material performance.

Test Results of Sintered Nanosilver Paste Die Attach for High-Temperature Applications

2016 ◽  
Vol 13 (1) ◽  
pp. 6-16 ◽  
Author(s):  
Paul Croteau ◽  
Sayan Seal ◽  
Ryan Witherell ◽  
Michael Glover ◽  
Shashank Krishnamurthy ◽  
...  
Keyword(s):  
High Temperature ◽  
Cooling System ◽  
Wide Band ◽  
Power Converter ◽  
Test Results ◽  
Wide Band Gap ◽  
Strain Behavior ◽  
Die Attach ◽  
Nanosilver Paste ◽  
Sintered Silver

The emergence of wide band gap devices has pushed the boundaries of power converter operations and high power density applications. It is desirable to operate a power inverter at high switching frequencies to reduce passive filter weight and at high temperature to reduce the cooling system requirement. Therefore, materials and components that are reliable at temperatures ranging from −55°C to 200°C, or higher, are needed. Sintered silver is receiving significant attention in the power electronic industry. The porous nature of sintered nanosilver paste with a reduced elastic modulus has the potential to provide strain relief between the die component and substrate while maintaining its relatively high melting point after sintering. The test results presented herein include tensile testing to rupture of sintered silver film to characterize stress-strain behavior, as well as die shear and thermal cyclic tests of sintered silver-bonded silicon die specimens to copper substrates to determine shear strength and reliability.

Reliability of Bonded Interfaces for Automotive Power Electronics

2013 ◽  
Author(s):  
Douglas DeVoto ◽  
Paul Paret ◽  
Sreekant Narumanchi ◽  
Mark Mihalic
Keyword(s):  
Thermal Resistance ◽  
Power Electronics ◽  
Carbon Fibers ◽  
Thermal Performance ◽  
Coefficient Of Thermal Expansion ◽  
Base Plate ◽  
Acoustic Microscopy ◽  
Thermal Cycles ◽  
Interface Materials ◽  
Sintered Silver

In automotive power electronics packages, conventional thermal interface materials such as greases, gels, and phase change materials pose bottlenecks to heat removal and are also associated with reliability concerns. There is an industry trend towards high thermal performance bonded interfaces. However, due to coefficient of thermal expansion mismatches between materials/layers and resultant thermomechanical stresses, adhesive and cohesive fractures could occur, posing a problem from a reliability standpoint. These defects manifest themselves in increased thermal resistance in the package. The objective of this research is to investigate and improve the thermal performance and reliability of emerging bonded interface materials for power electronics packaging applications. We present results for thermal performance and reliability of bonded interfaces based on thermoplastic (polyamide) adhesive, with embedded near-vertical aligned carbon fibers, as well as sintered silver material. The results for these two materials are compared to conventional lead-based (Sn63Pb37) bonded interfaces. These materials were bonded between 50.8-mm × 50.8-mm cross-sectional footprint silicon nitride substrates and copper base plate samples. Samples of the substrate/base plate bonded assembly underwent thermal cycling from −40°C to 150°C according to Joint Electron Devices Engineering Council standard Number 22-A104D for up to 2,000 cycles. The dwell time of the cycle was 10 minutes and the ramp rate was 5°C/minute. Damage was monitored every 100 cycles by acoustic microscopy as an indicator of an increase in thermal resistance of the interface layer. The acoustic microscopic images of the bonded interfaces after 2,000 thermal cycles showed that thermoplastics with embedded carbon fibers performed quite well with no defects, whereas interface delamination occurred in the case of sintered silver material. Both these materials showed a superior bond quality as compared to the lead-based solder interface even after 1,000 thermal cycles.

Study of Thermal Stress in Nano Silver Bonded Silicon Substrates for High Temperature Applications

2019 ◽  
Vol 2019 (HiTen) ◽  
pp. 000052-000055
Author(s):  
G.D. Liu ◽  
C.H. Wang
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Silver Layer ◽  
Silicon Substrates ◽  
The Finite Element Method ◽  
Nano Silver ◽  
Silicon Chips ◽  
Die Attach ◽  
The Relationship ◽  
Sintered Silver

Abstract The silver nanoparticle paste is a promising material for high temperature die-attach applications. In this paper, the finite element method is used to study the relationship between the thickness of the sintered silver layer and the thermal stress in the sintered silver joint. Silicon chips are bonded together with sintered silver layers of different thicknesses. In the experimental study, strain gauges are attached onto the surface of the upper silicon and used to estimate the effects of the nano silver die-attach layer. The results show that the average stress in the silver layer at the interface decreases with the increasing thickness of the silver layer, while the stress on the silicon surface increases with the increasing thickness of the silver layer.

Sintered Silver Die Attach with Extreme Thermal Stability for Extreme and Dynamic Environments

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000168-000176 ◽  
Author(s):  
Khalid Khtatba ◽  
Seyed Amir Paknejad ◽  
Ali Mansourian ◽  
Samjid H. Mannan
Keyword(s):  
High Temperature ◽  
Surface Oxidation ◽  
Migration Route ◽  
Oxidation Treatment ◽  
Contact Metallization ◽  
Die Attach ◽  
High Temperature Storage ◽  
Internal Pore ◽  
Temperature Storage ◽  
Sintered Silver

Abstract: The surface oxidation of internal pore surfaces of nano-scale sintered silver has increased stability for high temperature applications. After treatment, high temperature storage at 400 °C has resulted in no changes to microstructure. By contrast, it is known that the microstructure of untreated pressure-less sintered silver continuously evolves at temperatures above 200 °C. Grain and pore growth occur in this temperature range for conventional sintered silver resulting in coarsening of the microstructure and increased susceptibility to fatigue. However, oxidation treatment of the internal pore surfaces has the effect of freezing the microstructure when the contact metallization is also silver or chemically inert. Oxidation prevents mass transfer by shutting down the fastest atomic migration route along the internal pore surfaces. Samples exhibited no change in microstructure either through continuous observation through glass, or after cross sectioning. The tested specimens under high temperature storage resisted grain growth for the whole duration of the tests of more than 600 h at 300 °C. The only detectable changes in microstructure occurred in a sparse number of isolated grains (1 in 7000 grains), presumably due to non-penetration of oxidising treatment into these closed pore spaces. It is hypothesized that even these can be prevented by minor changes to the sintering paste to slightly increase initial porosity. The oxidising treatment can be performed via many different routes, such as exposure to steam, or even by dipping in water for 10 min.

Microstructure and Mechanical Properties of Pressureless Sintered Silver Die-attach Materials

2018 ◽  
Vol 2018 (1) ◽  
pp. 000602-000605
Author(s):  
Tomofumi Watanabe ◽  
Keisuke Tanaka ◽  
Masafumi Takesue
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Physical And Mechanical Properties ◽  
External Pressure ◽  
Exposure Test ◽  
High Temperature Exposure ◽  
Die Attach ◽  
Temperature Exposure ◽  
Substantial Change ◽  
Sintered Silver

Abstract Microstructural and mechanical properties of a pressureless sintered silver material were measured. The Microstructure of the pressureless sintered silver material had pores of less than 1 μm in size and some silver matrices sintered with nanoparticles between each other. The pressureless sintered silver material could be bonded on bare copper without applying an external pressure. After subjecting the material to a high temperature exposure test at 250 °C and for 1000 h, it showed no substantial change in microstructure and showed a constant Young's modulus of 14 GPa. The pressureless sintered silver material in this work did not show any embrittlement or increase in pore size after the high temperature exposure test, which demonstrated that the material has reliable physical and mechanical properties at temperatures up to 250 °C.

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